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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-941) Datanode xceiver protocol should allow reuse of a connection
Date Thu, 16 Jun 2011 18:19:49 GMT

    [ https://issues.apache.org/jira/browse/HDFS-941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13050621#comment-13050621
] 

Todd Lipcon commented on HDFS-941:
----------------------------------

Konstantin:
Yes, everything runs on one node. It tests the localhost path, which is identical to what
would be tested with your proposed benchmark (nrFiles <= nrNodes means full locality, right?).

bq. Also with 128 MB file everything is in RAM, not sure what it measures

It measures the overhead of DFS rather than the cost of IO. Having it *not* be in RAM makes
for a worse test since differences in CPU overhead are lost in the noise of the slow disks.

> Datanode xceiver protocol should allow reuse of a connection
> ------------------------------------------------------------
>
>                 Key: HDFS-941
>                 URL: https://issues.apache.org/jira/browse/HDFS-941
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: data-node, hdfs client
>    Affects Versions: 0.22.0
>            Reporter: Todd Lipcon
>            Assignee: bc Wong
>             Fix For: 0.22.0
>
>         Attachments: 941.22.txt, 941.22.txt, 941.22.v2.txt, 941.22.v3.txt, HDFS-941-1.patch,
HDFS-941-2.patch, HDFS-941-3.patch, HDFS-941-3.patch, HDFS-941-4.patch, HDFS-941-5.patch,
HDFS-941-6.22.patch, HDFS-941-6.patch, HDFS-941-6.patch, HDFS-941-6.patch, fix-close-delta.txt,
hdfs-941.txt, hdfs-941.txt, hdfs-941.txt, hdfs-941.txt, hdfs941-1.png
>
>
> Right now each connection into the datanode xceiver only processes one operation.
> In the case that an operation leaves the stream in a well-defined state (eg a client
reads to the end of a block successfully) the same connection could be reused for a second
operation. This should improve random read performance significantly.

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